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Old November 12th, 2013, 10:06 PM   #2241
scalziand
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All the pieces/modules that Broad uses are sized to fit on regular truck trailers.
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Old November 12th, 2013, 10:23 PM   #2242
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Was about say this. Size of the elements is actually one of few things that would work in ny. But there are just so many that wouldn't.

[IMG]http://i44.************/zlzzx1.jpg[/IMG]
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Old November 13th, 2013, 05:42 PM   #2243
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The picture from the post above is very useful to discuss about this controversial construction method, if is possible or not. I am not Structural Engineer, but EE, and I studied a bit of mechanics and I can say that I understand what happens in the picture above. At a first impression that crane has at least 30-40 tonnes without any load lifted. there are complex forces which act from crane support mast to building structure, both static and dynamic. first is a vertical component with a value almost equal with the weight of the crane plus load then there is lateral force which either pull or push the upper support depending on the position of the crane boom and if there is weight lifted of not. then is a shear force at the upper support created by the weight variation from load/unload condition. added to this there are forces caused by wind, weight lifting, load or unload as well oscillations of the mast, counterweights and the whole assembly.
All these forces are huge, with order of magnitude within 300-600kN or probably more in the worse case conditions. Suppose that the building from the previous post is made of prefabricated materials and no concrete or very little must be poured, it has to rise in record time and concrete takes at least few weeks to settle and gain it's default strenght, usually 28 days but we don't have that time, as we can see the building is rising few floors per day or per week ? then the floor slab seen on the trailer truck as well as underneath supporting beams are way too thin and fragile to be have enough tensile, bending and twisting strength to support the crane which is fixed on the outside wall. even the exterior wall which carries the vertical component of the weight might not be strong enough. It has probably thick steel piles but even so the structure is not robust enough because the upper side is unfinished yet and there is no closed polygon for return forces...
If I'm missing something, please someone clarify.
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Old November 14th, 2013, 12:52 PM   #2244
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I doubt 2/3 of the people who liked the above post, really understood a word of it
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Old November 14th, 2013, 01:26 PM   #2245
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Quote:
Originally Posted by AltinD View Post
I doubt 2/3 of the people who liked the above post, really understood a word of it
I didn't even read it
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Old November 14th, 2013, 03:47 PM   #2246
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I am not saying the post is incomprehensible
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Old November 14th, 2013, 04:58 PM   #2247
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TLDR....
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Old November 15th, 2013, 10:08 AM   #2248
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Quote:
Originally Posted by AltinD View Post
I am not saying the post is incomprehensible
Using simple words, that crane would peel the outer wall and fall to the ground like a stone if it has to be supported by such a fragile structure made overnight...
take a look at any other supertall UC and see that the cranes are supported on the massive core and the joints are connected to the inside columns and rebar. A building which claims to rise few floors once at 2 days or ever per day has barely enough strength to sustain itself. since it's good sense to consider that little or no concrete would be used, or even if large quantities would be used, this concrete will set days or even weeks after the floors above are being built.
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Old November 15th, 2013, 11:06 AM   #2249
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What you've said (in both your posts) was rather clear to me but it also is quite ungrounded. Because you see those building were actually build with prefabricated method and using this very crane - it's a fact. It doesn't of curse make definitive prove that the technology is feasible for 800m structure but as we only speak about the crane - it was there and it was fine On the picture below you can clearly see the prefabricated floor slabs were used.



Maybe what you are missing is the fact that except perimeter structure there are also similar structural walls inside the building (visible on the picture above) working like an inside structural truss. Also crane connectors are where the floor slabs are and close to the internal structural wall so there is more pulling forces than what it looked on the picture I posted on the top of that page, and as you must know steel is much more resistant to pulling forces than breaking forces. And lastly those floor slabs are not just thin steel sheets. They are quite a rigid structures by design capable of dealing both with pulling and compressive forces.

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Old November 15th, 2013, 01:04 PM   #2250
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Well, the problem is 'the 800 meters structure' and the speed they claim they will be able to build it.

PS: And of course, you weren't one of those 2/3 (or 3/3)
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Old November 15th, 2013, 01:21 PM   #2251
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The speed is already proven and the broad have done A LOT to prove their intention is really to build it.
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Old November 15th, 2013, 03:37 PM   #2252
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the speed is proven for a small scale, but lifting stuff up so many hundrets of meters and providing stability for such a large building will be a task in itself. i really really hope they do try to build what they promised, if problems cause them to delay further into construction that would be expected and wouldn't be too bad, the bad thing is that delays happen before it even starts.
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Old November 15th, 2013, 04:25 PM   #2253
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Quote:
Originally Posted by patrykus View Post
The speed is already proven
How, where, when .... since when did they already built a 800+ meters tall building?
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Old November 15th, 2013, 04:28 PM   #2254
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Quote:
Originally Posted by crriss View Post
Using simple words, that crane would peel the outer wall and fall to the ground like a stone if it has to be supported by such a fragile structure made overnight...
take a look at any other supertall UC and see that the cranes are supported on the massive core and the joints are connected to the inside columns and rebar. A building which claims to rise few floors once at 2 days or ever per day has barely enough strength to sustain itself. since it's good sense to consider that little or no concrete would be used, or even if large quantities would be used, this concrete will set days or even weeks after the floors above are being built.
I doubt any concrete will be used for the major structural elements. Concrete just isn't compatible with such a fast construction which they claim. I think this will be an all steel tower. I can only imagine a layer of concrete used on the floors slabs

According to the picture patrykus posted this should have a bundled tube structure like the Willis Tower. In the 70s all skyscrapers were only steel and they didn't have problems with cranes so I think this won't be an issue in this case either. In fact, the old WTC or the Aon Center in Chicago were just a tube, not a bundled tube, so they needed even more support to hold their cranes but floor trusses can provide it. These trusses gained bad reputation in the earlier stages of 9/11 investigation where it was believed that their failure might have triggered the collapse, but in later works it was found out, that the opposite was true, the fact that they didn't fail, only bent meant that they bent the perimeter columns and that was what caused the collapse. But to the topic at hand, I think floor trusses will be enough to support a tower crane in this building ........ that is if construction starts
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Old November 15th, 2013, 04:45 PM   #2255
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Quote:
Originally Posted by AltinD View Post
How, where, when .... since when did they already built a 800+ meters tall building?
I said SPEED is proven not that they can build 800m tower with it. But anyway they spent too much just not to build it.
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Old November 15th, 2013, 07:10 PM   #2256
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if i can run 100m in under 10 seconds, doesn't mean i can run 600m in under a minute. lifting stuff 800m upwards and a strong wind and a lot of problems may delay what they know how it works on ground level.
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Old November 15th, 2013, 07:44 PM   #2257
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if i can run 100m in under 10 seconds, doesn't mean i can run 600m in under a minute. lifting stuff 800m upwards and a strong wind and a lot of problems may delay what they know how it works on ground level.
Exactly
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Old November 15th, 2013, 08:39 PM   #2258
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A few months ago I mentioned in this thread that I find the idea of a 700-something-meter box withstanding wind pressure and its own weight without a solid core very unrealistic, and I got a massive shitstorm in response, "OH NO, YOU'RE WRONG, THEY DID TESTS!!!" Now I come back to this thread and everything is still the same...
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Old November 15th, 2013, 08:45 PM   #2259
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Quote:
Originally Posted by KillerZavatar View Post

if i can run 100m in under 10 seconds, doesn't mean i can run 600m in under a minute. lifting stuff 800m upwards and a strong wind and a lot of problems may delay what they know how it works on ground level.
Wrong analogy People get tired fast, and as we know from construction sites speed of construction doesn't change much for repetitive floors during timeline of the project. Actually it's often the opposite. Construction speed increase in later phases as logistics gets simpler at the base. And for this particular shape it's rather obvious that for the same amount of cranes even if lifting will get a little bit longer on later phases decreasing floor space at upper levels will compensate for that.

Anyway the bottom line is that IF construction speed will vary much at all it can't be by more than 50% I'd say. So for this construction technique that would mean that instead of 2.5 floors per day they would make "only" 1 and 800m tower would still take less than a year to build. So yeah the speed of the technology is already well proven. The only remaining thing to prove is if they can rise 800m tower with it. And if they can do it with showcased technology then there is no doubt it will be several times faster than with the conventional methods even if it will take much longer than proposed 90 days.
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Old November 15th, 2013, 08:50 PM   #2260
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Quote:
Originally Posted by KillerZavatar View Post

if i can run 100m in under 10 seconds, doesn't mean i can run 600m in under a minute. lifting stuff 800m upwards and a strong wind and a lot of problems may delay what they know how it works on ground level.
Broad Group built that 30-floor hotel in 15 days, at the rate of 2 floors a day.
Broad Group is attempting to build the new 220-floor Sky City in 90 days.
That will be at a planned rate of 2.5 floors a day.

So I think if one can run 100m in 10 seconds, using the same math, Broad will be able to run 600 FASTER in 49 secs.

Tell you what, I am truly rooting for Broad Group to go for it!
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